Railway traffic controlling apparatus



Aug. 2, 1932. o. GRONDAHL 1,

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed April 15, 1931 3Sheets-Sheet 1 Fzlgt N ATTORNEY Aug. 2, 1932. Y L. o. GRONDAHL 1,869,847

RAILWAY TRAFFIC CONTROLLING" APPARATUS Filed April 15, 1931 3Sheets-Sheet 2 INVENTOR; N L-O.G/-onb n/1/,

BY i M ATTORNEY Aug. 2, 1932. L. o. GRONDAHL 1,869,847

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed April 15, 1951 sSheets-Sheet 5 y 5 I INVENTOR.

L 0. Graham/N,

Q "pt W ALQ ATTORNEY.

Patentd Aug. 2, 1932 UNITED STATES PATENT OFFICE LABS O. GRONDAHL, OFPITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY,OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA Applicationfiled April 18,

My invention relates to railway traflic controlling apparatus, andparticularly to cab signaling or train control systems of the codedcontinuous inductive type.

One feature of my invention is the provision in systems of thischaracter of means for supplying the track rails with alternatingcurrents of different frequencies periodically interrupted or coded atone and the same frequency, together with train-carried apparatusselectively responsive to the several coded currents thus applied to therails.

I will describe two forms of trackway apparatus and one form oftrain-carried apparatus, all embodying my invention, and will then pointout the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing oneform of trackway apparatus embodying my invention. Fig. 2 is adiagrammatic view showing a modification of a portion of the trackwayapparatus shown in Fig. 1. Fig. 3 is a diagrammatic view showing oneform of train-carried apparatus embodying my invention.

Similar reference characters refer to similar parts in each of theviews.

Referring first to Fig. 1, the reference characters 1 and 1" designatethe track rails of a railway track along-which trafiic normally moves inthe direction indicated by the arrow. These rails are divided byinsulated joints 2 into a plurality of successive blocks or sections, ofwhich only three complete sections, AB, B-C and CD, are shown in thedrawings. Extending along the railroad track are three transmissionlines 5, 6 and 7, which are constantly supplied with alternatingcurrents of diflerent frequencies, such, for example, as 60 cycles persecond, 80 cycles per second, and 130 cycles er second, respectively.Associated with eac track section are three transformers T, U and V, theprimaries 4 of which are connected with the transmission lines 5, 6 and7, respectively, and the secondaries 8 of which are utilized to supplycurrent to the track rails and to other apparatus associated therewith,as hereinafter explained.

RAILWAY TRAFFIC CONTROLLING APPARATUS 1931. Seriali No. 529,723.

Each tracksection is pro'videdwith two track relays Q and B. Each relayQ is a. slow-releasing direct current relay, and its winding isconnected across the rails through the medium of a full-wave rectifierX. Each relay R is of the alternating current type,

having a winding 8 connected across the rails of the section and asecond winding 9'constantly supplied with alternating current codingdevice is controlled by a normally deenergized coder relay K.

As shown in the drawings, the section immediately to the right of pointD is occupied by a train W, so that both track relays Q, and R for thissection are de-energized. Alternating current of reverse relativepolarity is therefore supplied to the rails of section C-D, the circuitbeing from the right-hand terminal of secondary 3 of transformer T,through contact 12d of relay R, to the upper track rail 1, and from thetrack rail 1, through back contact 11 as relay K, and the middle contact10-03 of relay R, to the lefthand terminal of secondary 3 of transformerT Inasmuch as winding 8 of track relay R is supplied with cycle currentof reverse relative polarity, and winding 9 of this relay is alsosupplied with 60 cycle current, this relay is energized in its reversedirection, so that its contact fingers are swung to the left. Relay Q isalso energized, but this fact is of no immediate importance. Sixty cyclecurrent of normal relative polarity is now supplied to the rails ofsection B-C, the circuit being from the right-hand terminal of secondary3 of transformer T through contact 127' of relay R back contact 11 ofrelay K to the lower rail 1, and from the upper rail 1, through contact10r of relay Rf, to the left-hand terminal of the secondary oftransformer T. This current serves to energize relay R inthe normaldirection, and it also serves to energize track relay Q". Sixty cyclecurrent of normal relative polarity is therefore supplied to the railsof section AB, the circuit being from the right hand terminal ofsecondary 3 of transformer T through contact 12-% of relay R backcontact 11 of relay K to the lower track rail 1", and from the uppertrack rail 1, through contact 10'n of relay R ,'to the left-handterminal of secondary 3 of transformer T Track relay R is thereforeenergized in the DQ113511 direction and relay Q} is also energlze I willnow assume that a train moving toward the right passes through thestretch of track shown in the drawings. When this train enters sectionAB, it will open both track relays Q and R with the result that coderrelay K will become energized, the circuit being from the right-handterminal of secondary 3 of transformer T through the winding of relay Kback contact 14 of relay Q ,-and back contact 13-03 of relay R to theleft-hand terminal of the secondary of transformer T Motor M will thenbe energized, the circuit being from the right-hand terminal ofsecondary 3 of transformer T through the motor M and front contact 15 ofrelay K to the left-hand. terminal of the same secondary. -The openingof back contact 11 of relay K will open the circuit previously tracedfor the supply ofrcurrent to the rails of section A-B, from transformerT and the closing of contact 19 of this relay will close a new circuit,this circuit being from the right-hand terminal of secondary 3 oftransformer T through normal contact 20n of relay R front contact 19 ofrelay K coder contact 18 to the lower rail 1*, and from the upper rail1, through coder contact 17 and normal contact 16-n of relay R to theleft-hand terminal of secondary 3 of transformer T Sixty cycle currentperiodically interrupted at the rate of 2 cycles per second willtherefore be supplied to the rails of section A-B, and as hereinafterexplanned, this current will produce what may e termed the high speedsignal on the train octu pying this section.

en the front end of the train enters sec-.

tion BG it will de-energize track relays Q and R and this will causerelay K to become energized by virtue of a circuit which rentperiodically interrupted at the rate of 2 cycles per second will besupplied to the rails of this section from transformer U The circuit forthis current is from the righthand terminal of secondary 3 oftransformer U, through reverse contact 20-4 of relay R front contact 19of relay K,coder contact 18,

to the lower rail 1, and from the upper rail -1, through coder contact17 and reverse conentrance of the train into section B-C, willdiscontinue the supply of coded cycle current to the rails of sectionAB, and will cause coded 130 cycle current to be supplied to the railsof this section, the circuit being from the right-hand "terminal ofsecondary 3 of transformer V through contact 16d of relay R contact 17of coding device P to the upper rail 1, and from the lower rail 1",through contact 18 of coding device P front contact 19 of relay K andcontact 20-11 of relay R to the left-hand terminal of secondary 3 oftransformer V When the rear end of the train passes out of section AB,this coded 130 cycle current will serve to energize relay Q his willopen the circuit for relay K with the result that 60 cycle currentofreverse relative polarity will be supplied to the rails of section AB,thereby energizin relay R in the reverse direction.

When t e front end of the train enters section C-D, it will de-energizerelays Q and R thereby energizing relay K and so setting motor M intooperation. The supply of 60 cycle current to the rails of section (J-Dwill then be discontinued, and coded 130 cycle current will be suppliedto the rails of this section, the circuit being from the righthandterminal of secondary 3 of transformer Vflthrough contact 16d 'of relayR, contact 17 of coding device P to the upper rail 1 and from the lowerrail 1 through codin contact 18, front contact 19 of relay K. an contact20-d of relay R to the left-hand terminal ofsecondary 3 oftransformer V.This current will give what maybe termed a low speed indication? on thetrain occupy ing section CD.

The opening of relays Q? and R due to the entrance of the train insection CD,

will cause coded 130 cycle current to be supplied to the rails ofsection BC, and when. the rear end of the train leaves the lattersection, this coded current will serve to energize track relay Q therebyde-energizing relay K and so stopping the operation of motor M andcoding device P ninterrupted 60 cycle current will then be supplied tothe rails of section B-C, so that relay R will become energized in thereverse direction.

When the front end of the train enters the section to the right of pointD, it will have no effect on the apparatus associated with this section,because the section is already occupied by the advance train W, and thesecond train will receive no energy from the track rails, because suchenergy is shunted by the wheels and axles of the train W.

Referring now to Fig. 2, the apparatu shown in this view is similar tothat shown in Fig. 1, except that there is only one transmission line27, and the train-controlling currents are furnished by localgenerators, which are, in turn, furnished with energy from thistransmission line. Preferably the transmission line carries alternatingcurrent at 60 cycles per second. Each section is provided with atransformer N, the primary 26 of which is connected with thetransmission line 27, and the secondary of which is connected with theinput terminals of a fullwave rectifier H. Each secondary 25 alsofurnishes uninterrupted 60 cycle track circuit current for theassociated section.

The local generators are designated E, F and G, and each of thesegenerators comprises a relay 3O controlling the supply of current to aprimary 21, 22 or 23 of a transformer S. The secondary 24 of thistransformer furnishes coded current to the rails of the associatedsection when the section-is occupied by a train.

As shown in the drawings, the section to the right of point D is occuied by a train W, so that both track relays 4 and R are deenergized.Sixty cycle current of reverse relative polarity is supplied to therails of section CD in the same manner as in Fig. 1, that is, thiscircuit includes secondary 25 of transformer N contact 12d of relay Rback contact 11 of relay K, and contact 10- d of relay R Relay R istherefore energized in the reverse direction, with the result that 60cycle current of normal relative polarity is supplied to the rails ofsection B-C. Relay R is therefore energized in normal direction, so that60 cycle current of normal relative polarity is supplied to the rails ofsec- %on AB from secondary 25 of transformer I will now assume that atrain moving toward the right passes through the stretch of track shownin the drawings.

When thistrain enters section A-B,it will de-energize relays Q and Rthereby causing relay K to become energized, and this in turn willenergize motor M from transformer N Relay'30 of coding device E is nowenergized, the circuit being from the upper'terminal of rectifier Hthrough contact 16n of relay R winding of relay 30, back contact 31 ofthis relay, contact 20-n of relay R to the lower terminal of rectifier HA reactor 29 is connected in series in this circuit, and a condenser 28is connected across the output terminals of rectifier H the purpose ofthese elements being to smooth out the direct current supplied to relay30. Owing to the fact that the circuit for relay 30 includes a backcontact of this relay, it follows that the contact will vibrate,

thereby alternately closing contact 31-?) and contact 3l-0. Contacts 5and 0 are connected to the outer terminals, respectively,

of primary 21 of transformer S and the middle point of this ,primary isconnected with the upper terminal of rectifier H through contact 16-02of relay R Contact 31 is, of course, connected with the lower terminalof rectifier H and so it follows that while relay 30 is in operation,current will alternately be supplied to the upper and lower halves ofprimary 21, with the result that alternating current will be deliveredby the secondary 24 of transformer S The parts of the generator E? areso proportioned that this current will have a frequency of cycles persecond. This current will be delivered to the rails of section A-B,through the contacts of coder P, the circuit being from the upperterminal of secondary 24, through front contact 19 of relay K codercontact 18, to the lower rail 1, and from the upper rail 1, throughcoder contact 17 to the lower terminal of secondary 24. The trainoccupying section A-B will therefore receive coded 6O cvcle current, andthis current will cause the high speed indication to be given on thetrain.

When the train enters section BC, it will deenergize track relays Q, andR thereby energizing relay K Inasmuch as relay R is energized in thereverse direction, generator F is in operation, its circuits beingclosed by contacts 20-1' and 161' of relay R and the parts of thisgenerator are adjusted to deliver 80 cycle current to the transformer Sso that coded 8O cycle current will be supplied to the rails of sectionB-C. This will cause the medium speed indication to be given aboard thetrain. When the train enters section CD, it will de-energize relays Rand Q thereby energizing relay K, and since relay R is de-energized,generator G will be in operation, because its circuits will be closed atcontacts 20-03 and 16-11 of relay R. This generator is adjusted todeliver 130 cycle current to the transformer S and so coded 130 cyclecurrent will be furnished to the rails of section C-D to cause the low Ginto operation, so that coded 130 cycle' current will then be suppliedto the rails of section A-B.' This will cause relay Q to becomeenergized, thereby de-energizing relay K with the result thatuninterrupted 6O cycle current of reverse relative polarity will besupplied to the rails of section A-B. This Wlll cause relay R to becomeenergized.

A similar operation will occur as the train passes from section BO tosection C-D.

Referring now to Fig. 3, the train-carried apparatus in the form hereshown, comprises two magnetizable cores 33 and 33, mounted in front ofthe forward axle and disposed above the two track rails 1 and 1",respectively. These cores carry windings 35 and 35*, which are connectedin series in such manner that the alternating currents induced thereinby an alternating current flowing in opposite directions in the twotrack rails 1 and 1 at any given instant, are additive. This circuitconstitutes the input circuit for an amplifier Y, the output circuit ofwhich is provided with three multiple branches if), L and L Each branchincludes a reactor 37 and a condenser 36, and these elements are soadjust/ed that the three branches L L and L are tuned respectively at 60cycles, 80 cycles and 130 cycles per second.

Connected across a portion of the reactor I 37 of branch L is a relay 9having a contact 39 which contact is tuned mechanically to resonance atcycles per second,- and this contact cooperates with two fixed contactmembers 39 and 39 The primary 41' of transformer t is provided with acircuit which includes a battery 40, contacts 39--39 and 39-39 inmultiple and the primary 41, this primary being tuned by a condenser 42to resonance at 60 cycles per second. lit follows that when coded 60cycle current is being received by the train, periodically interruptedalternating current ,will be delivered by the secondary 43 oftransformer 6 but that substantially no alternating current will bedelivered by this secondary under any other condition. The secondary 43is provided with an output circuit including a condenser 45 "and areactor 44, whereby this circuit is tuned to the code frequency, thatis, the frequency of the periodic interruptions of the current deliveredby secondary 43. The input terminals of the full-wave rectifier k areconnected across a portion of the reactor 44, and a slow-releasing relayu is connected with the output terminals of this rectifier. It followsthat relay u will be periodically energized when coded 6O cycle currentis being received by the train, but that this relay will not beenergized under any other circumstances. Owing to the slow-releasingcharacteristic of relay to, the relay will remain closed during thesupply of coded 60 cycle currents.

Branch L is (provided with a relay 9 mechanically tune to resonance at80 cycles per second, and associated with the armature of this relay isa transformer t the secondary 43 of which is connected with theoperating sen, filed Feb. 7,1930, Serial No. 426,563, for

circuit including a battery 53 and a primary 54 of a transformer n. ThisperiodiE supply of direct current to the primary 54 causes analternating current in the secondary 55, the frequency of which currentcorresponds to the frequency of the code. A slow-releasing relay u isconnected with secondary 55 through a full-wave rectifier 7L with theresult that relay u isperiodical'ly energized by direct current when theoscillator J is in operation. A condenser 56 is connected across theterminals of secondary 55 to maintain the flow of current in thesecondary circuit during the periods in which contact 52-52 is open.Relay if being slow-releas- 4 ing in character, will keep its frontcontacts closed as long as coded 8O cycle current is being received onthe train.

Referring now to branch L of the receiving circuit, the input terminalsof a rectifier f are connected across a portion of the reactor 37, andthe output terminals of this rectifier are connected with the primary 59of a transformer 6 It follows that this primary is supplied with directcurrent which is periodically interrupted at the code frequency, andthis current induces an alternating current of code frequency insecondary 60. The circuit for secondary 60 includes a reactor 61 and acondenser 62 by means of which the circuit is tuned at the codefrequency, and the input terminals of a full-wave rectifier b areconnected across a portion of the reactor 61. A slow-releasing relay'uis connected with the output terminals of this rectifier, whereby thisrelay is periodically su plied with direct current when coded 130 cyc ecurrent is being received on the train. I

When relay 2& is energized, a lamp 48 is lighted, thecircuit being froma battery 47,

through ,front contact 46 of" relay u, andthe lamp 48 to battery 47 Thislamp may be .utilized to give the high speed indication. When relay u isenergized its contact 57 closes a similar circuit for a lamp 58, whichmay give a medium speed indication. When relay u is energized, itscontact 63 closes a. similar circuit through a third'lamp 64, which may've a low speed indication. .When all of t e relays u are'de-energized,a fourth lamp 142 will be lighted, the circuit for which lamp includesback contacts 139, 140 and 141' of relays u n and u respec tively. Thislamp, when lighted, may give a stop indication, and it will be notedthat this lamp will be lighted when and only when there is no codedalternating current being received by the train.

Although I have herein shown and described only certain forms ofapparatus embodying my invention, it is understood that various changesand modifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention;

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track divided into a pluralityof sections, means controlled by a train in one of said sections forsupplying periodic currents of different frequencies to each of certainothers of said sections, and means controlled by a train in each of saidcertain other sections for coding the current supplied to such section.

2. In combination, a stretch of railway track divided into a pluralityof sections, means controlled by a train in one of said sections forsupplying a periodic current of a difierent frequency to each of severalother sections in the rear thereof, and means controlled by a followingtrain in one of said other sections for coding the current in thesection occupied thereby.

3. In combination, a stretch of railway track divided into a pluralityof sections, means controlled by a train in one of said sections forsupplying an alternating current of a different frequency to each ofseveral other sections in the rear thereof, and means associated witheach of said sections and successively controlled by said followingtrain for interrupting said currents of different frequencies accordingto a common code as said following train proceeds from one of said othersections to another.

4. In combination, ,a stretch of railway track divided into a pluralityof sections, a plurality of sources of periodic currents of differentfrequencies, means controlled by a train in one of said sections forpartially establishing a circuit for each of several of said sections,in the rear thereof, each of said circuits including the source of oneof said currents, means controlled by a following train for completingthe circuit for the section occupied thereby, and means controlled bysaid following train for interrupting the current in each of saidsections according to a common code.

5. In combination, a stretch of railway track, means for selectivelysupplying the track' rails of said stretch with alternating currents ofdifferent cyclic frequencies periodically varied at the same codefrequency, and a plurality of governing devices all controlled by energyreceived from the track rails and tuned to both electrical resonance atsaid cyclic frequencies and mechanical resonance at said codefrequencies.

ing device controlled by each of said auxiliary relays, means controlledby a first train in a first one of' said sections for establishing acircuit for one of said currents including a second section and thecoding device for said second section. a circuit for another of saidcurrents including a third section and the coding device for said thirdsection, and a circuit for still another of said currents including afourth section and the coding device, for said fourth section.

7. In combination, a stretch of railway track divided into a pluralityof sections, a plurality of sources of alternating current of differentfrequencies, a three position track relay associated with each of saidsections, an auxiliary relay controlled by each of said track relays, acoding device controlled by each of sald auxiliary relays, a circuit fora first section including the source of one of said currents and anormal contact of one of said track relays as well as a front contact ofone of said auxiliary relays and one of said coding devices, a circuitfor a second section including the source of another of said currentsand a" reverse contact of another of said track relays as well as afront contact of another of said auxiliary relays and another of saidcoding devices, and a circuit for a third section including the sourceof still another of said currents and a middle contact of still anotherof said track relays as well as a front contact of still another of saidauxiliary relays and still another of said coding devices.

8. In combination, a stretch of railway track divided into a pluralityof sections, a plurality of sources of currents of differentcharacteristics, a three position track relay associated with each ofsaid sections, a direct current track relay associated with each of saidthree position relays, an auxiliary relay controlled jointly by saidtrack relays for each of said sections, a coding device con trolled byeach of said auxiliary relays, a circuit for a first section includingthe source of one of said currents and a normal contact of one of saidtrack relays as well as a front contact of one of said auxiliary relaysand cuit for a third section including the source 1 of still another ofsaid currents and a middle contact of still another of said track relaysas wellas a front contact of still another of said auxiliary relays andstill another of said I coding devices.

- '9. In combination, a stretch of railway track divided into aplurality of sections, a plurality of sources of currents of difierentcharacteristics, a three position track relay associated with each ofsaid sections, a direct current track relay connected in parallel witheach of said three position relays, an auxiliary relay associated witheach of said sections, a circuit for controlling each of said auxiliaryrelays including a source of one of said currents and a middle contactof one of said three position relays as well as a back contact of theassociated direct current relay, a coding device associated with each ofsaid sections, a control circuit for each of said coding devicescontrolled by a front contact of one of said auxiliary relays, a circuitfor a first section including the source of one of said currents and anormal contact of one of said track relays as well as a front contact ofone of said auxiliary relays and one of said coding devices, a circuitfor a second section including the source of another of said currentsand a reverse contact of another of said track relays as well as a frontcontact of another of said auxiliary relays and another of said codingdevices, and a circuit for a third section including the source of stillanother of said currents and a middle contact of still another of saidtrack relays as well as a front contact of still another of saidauxiliary relays and still another of said coding devices.

10. In combination, a stretch of railway track, means for supplyingcurrents of difierent characteristics to said stretch, means forinterrupting said currents at a predetermined frequency, a plurality ofsignals carried by a train, and means responsive to both thecharacteristics of' said currents and the frequency of saidinterruptions for selectively controlling said signals.

11. In combination, a stretch of railway track, means for supplyingalternating currents of different frequencies to said stretch,

I means for interrupting each of said currents at a predetermined codefrequency, a plurality of signals carried by a train, a plurality ofcircuits each tuned to resonance at the frequency of one of saidcurrents for controlling certain of said signals, and means tuned tosaid code frequency for controlling said signalsjointly with saidcircuits.

12. In combination, a stretch of railway track, means for supplyingalternating currents of different frequencies to said stretch,

, means for interrupting each of said currents at a predeterminedfrequency, a plurality of signals carried by a train, a first circuittuned to resonance at the frequency of one of said currents forcontrolling one of said signals, a second circuit tuned to resonance atthe frequency of said interruptions for controlling said signal jointlywith said first circuit. a third circuit tuned to resonance at thefrequency of another of said currents for aeeaecr controlling another ofsaid signals, and a fourth circuit tuned to resonance at the frequencyof said interruptions for controlling said last mentioned signal jointlywith said third circuit.

13. In combination, a stretch of railway track, means for supplyingalternating currents of diflerent frequencies to said stretch,

means for interrupting said currents at a predetermined frequency, aplurality of signals carried by a train, a plurality of circuits eachtuned to resonance at the frequency of one of said currents forcontrolling certain of said signals, and a device mechanically tuned tooscillate at a natural frequency equal to that of said'interruptions forcontrolling one of said signals jointly with the tuned circuitassociated therewith.

' Id. In combination, a stretch of railway track, means for supplyingalternating currents of difierent frequencies to said stretch, means forinterrupting said currents at a predetermined frequency, a plurality ofsignals carried by a train, a plurality of circuits each tuned toresonance at the frequency of one of said currents for controllingcertain of said signals, a contact device for controlling one of saidsignals jointly with the tuned circuit associated therewith, and adevice mechanically tuned to operate at a natural frequency equal tothat of said interruptions for controlling said contact device.

15. In combination, a stretch of railway track, means for supplyingalternating currents of different frequencies to'said stretch, means forinterrupting said currents at a predetermined frequency, a plurality ofsignals carried by a train, a slow acting relay for controlling one ofsaid signals, a circuit for controlling said relay, a contact forcontrolling said circuit, a device mechanicallytuned to oscillate at anatural frequency equal to that of said interruptions for controllingsaid contact, and a circuit tuned to resonance at thefrequency of one ofsaid currents for controlling said device.

16. In combination, a stretch of railway track divided into sectionsA-B, B-C and C-D, means controlled by a train in section B-C for.supplying periodic current of a certain frequency to section A-B, meanscontrolled by'a train in section 0-1) for supplying periodic current ofa different frequency to section AB, and means controlled by a train insection AB for interrupting botih of said currents according to a commonco e.

17. In combination, a stretch of railway track divided into sectionsA-B, B0 and CD. means controlled by a first train in section BC forsupplying periodic current of a certain frequency to section AB, meanscontrolled by said first train when it proceeds into sections-C'D forsupplying periodic current of a' different frequency to section A-B,means controlled by said first train when it departs from section C-Dfor supplying periodic current of still another different frequency tosection A-B, and means controlled by a train in section A-B forinterrupting all of said currents according to a common code.

18. In combination, a stretch of railway track vdivided into a pluralityof sections,

means controlled by a first train as it proceeds through certainsuccessive sections for supplying periodic currents of differentfrequencles to a certain other of said sections in the rear thereof, andmeans controlled by a second train in said certain other section forinterrupting each of said currents according to a common code.

In testimony whereof I aflix my signature.

LARS 0. GBONDAHL.

